Manuscripts and Special Collections

Introduction to Weights and Measures

Engraving of a pair of scales in a shop, from The Child's Arithmetic: A Manual of Instruction for the Nursery and Infant Schools (London: William S. Orr and Co., 1837)

Deciphering units of weights, measurements, and money in historical documents can cause problems for researchers.

Virtually every unit of measurement used up to the mid-twentieth century has now been replaced, or is being replaced, by decimal or metric measurements. A few old measurements are still in current use in the UK, such as pints and miles, but most people will now need to consult reference works in order to understand the measurements used in the past.

The information provided within this skills unit aims to identify and explain some of the most common difficulties and pitfalls and to provide sources of assistance. It is concerned only with English and Welsh measurements. Researchers should check specialist publications and the Scottish Archives Network (SCAN) Weights and Measures Guide for information on Scottish measurements.

Standardisation of weights and measures in England and Wales was a long and complicated process. The measurements referred to here are predominantly those used from the late sixteenth and early 17th centuries onwards, and those in force after the Weights and Measures Act of 1824. For medieval and earlier measurements, researchers should consult specialist works.



Imperial and Metric measurements

Imperial measurements were derived from the measurements used by the Romans. Over time, measurements used by different countries began to vary. For instance, the standard Imperial measurements used in Scotland were different from those used in England and Wales.

The Metric system was developed by the French and was enforced there in 1795. It bases all measurements on decimal divisions - dividing units into ten. The word 'metric' comes from 'metre', the French unit of linear measure. The system is now officially called the Système International d'Unités, or SI.

Metric measurements were gradually adopted by other countries. In 1969 the UK government began a process of phasing out Imperial measures, but progress has been slow. Most pre-packed goods have been sold in Metric measurements (kilos, grams and litres) since 1995. On 1 January 2000 it became illegal to sell loose goods such as fruit and vegetables in Imperial measurements (pounds and ounces). The exception to the rule is draught beer which is still sold in pubs in pints. Milk is also still sold in pint-sized containers, although they are officially measured in litres.

Area and linear measurements are also at a half-way stage. Acres have made way for hectares, and most measurements are now officially calculated in metres and centimetres. However, roads and speeds are still measured in miles rather than kilometres. Despite these legal changes, most people still use Imperial measurements in everyday conversation and to describe their own height and weight. However, they may not be aware of all the archaic measurements which appear in historic documents.

Throughout the unit, illustrative images are taken from the collections held by Manuscripts and Special Collections at the University of Nottingham.

This unit was written in August 2006.


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Manuscripts and Special Collections

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